Czochralski growth and characterization of TbxGd1−xScO3 and TbxDy1−xScO3 solid-solution single crystals

TbxGd1−xScO3 and TbxDy1−xScO3 solid-solution single crystals were grown by the Czochralski method to validate the practicality of solid solutions between neighboring RE scandates (REScO3). Within this material family, it is demonstrated that fine-tuning the pseudo-cubic lattice parameters between nearly all endmembers is now possible by adjusting the chemical composition of the mixed crystals. Film-tailored substrate lattice spacings enable fine adjustments of epitaxial strain or the growth of nearly strain-free heteroepitaxial films. Investigations of the chemical composition of the grown crystals revealed low segregation, which qualifies the solid-solutions as suitable substrate materials. The melting behavior was studied by differential thermal analysis. To calculate the thermal conductivity, λ(T), the heat capacity and thermal diffusivity were measured by differential scanning calorimetry and the laser flash technique, respectively. It was found that the thermal conductivity shows a minimum near 900 K and increases untypically at higher temperatures.2868287

Structural Evolution from 0D Units to 3D Frameworks in Pb Oxyhalides: Unexpected Strongly Corrugated Layers in Pb 7 O 6 Br 2

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Structural Evolution from 0D Units to 3D Frameworks in Pb Oxyhalides: Unexpected Strongly Corrugated Layers in Pb₇O₆Br₂

Novel Pb₇O₆Br₂ (<b>1</b>) lead oxybromide was prepared from Pb oxybromide melt by the “rapid quenching” route. Bonding scheme, thermal expansion, and structural properties were studied. The structural features of this unexpectedly complex phase are described on the basis of lone electron pair stereochemical activity and Pb–Br versus Pb–O bonding scheme. The structure of <b>1</b> contains a number of cavities, which can be assigned to the self-containments of the lone electron pairs on Pb²⁺ cations. “Empty” □Pb₄ chains are observed in between of the folding sides of the adjacent strongly corrugated oxocentered [Pb₇O₆]²⁺ layers. Highly isotropic thermal expansion of <b>1</b> appeared to be unexpected. The possible explanations of such a behavior in <b>1</b> are given. The structure of <b>1</b> is an interesting example of tetrahedral framework with mixed chemical bonding and is the densest known among Pb oxyhalides with the density of 18.4 tetrahedra/1000 ų. Current study shows that oxocentered layers derivatives from α-PbO can be very flexible and form rather dense three-dimensional structural topologies. The properties and structure are compared to other phases crystallizing in the anhydrous PbO–Pb<i>X</i>₂ (X = F, Cl, Br, I) systems, illustrate the complexity of lead oxyhalides, and reveal new and general pathways for the targeted synthesis of new phases with the Pb–O units of desired dimensionality. The indirect gap value of ∼2.04 eV obtained from generalized gradient approximation calculations demonstrates potentially good photocatalytic properties of <b>1</b>